Endoscope optical system

ABSTRACT

An endoscope optical system comprising rod lenses between the objective and ocular lenses has the feature that gradient rod lenses, whose lengths each end centrally between two intermediate images, are installed with small spacings between the ocular and objective lenses. To this end, the rod lenses terminate centrally between two intermediate images and the distal and proximal gradient rod lenses have no more than half the length of the spacing between said intermediate images.

BACKGROUND OF THE INVENTION

The invention relates to an endoscope optical system comprising anobjective and an ocular lens and intermediate rod lenses, with anoptional number of intermediate images.

DESCRIPTION OF THE PRIOR ART

Endoscope optical system of aforesaid kind, e.g. according to GermanPat. No. 2,305,473 have the advantage thanks to their structure, thatthe number of glass-air interfaces is reduced considerably and that thelight losses are kept to a minimum thereby.

It is also known that a single thin rod lens through which the lightbeams pass under sinusoidal curvature may be utilised in endoscopes as agradient rod lens, to considerable advantage. Such single rod lenses arevery liable to break and repairs involve considerable expense and longerstoppage periods in the utilisation of the endoscope.

SUMMARY OF THE INVENTION

It is an object of the invention to modify and construct endoscopescomprising single thin gradient rod lenses in such manner as to preventbreakages.

In an endoscope according to the invention, this object is achieved inthat an image transmitter comprising single essentially known gradientrod lenses which are set at minimum distances and whose lengthsterminate between two intermediate images, is situated between theocular and objective lenses.

Breakages of the optical system comprising gradient rod lenses areeliminated thanks to this solution, since the spacing span between twogradient rod lenses in each case may be shifted to the points at whichflexure or breaking stresses may occur. This is possible because thelengths of the individual rods may be selected freely as a function ofthe individual spacings between the intermediate images. It isparticularly advantageous however if the lengths of the gradient rodsare equal to that of the intermediate image spacing and the gradient rodlenses terminate centrally between two intermediate images, whereas theproximal and distal gradient rod lenses have a length corresponding tono more than half the distance between two intermediate images.

The maximum amplitudes of the sinusoidally extending beams are therebyplaced in the spacing span between two gradient rod lenses in each case,i.e. the beams have their greatest divergency at these points, so thatany dust particles or the like which may be present disturb the image asa whole to a minimum extent for this reason.

Furthermore, the solution according to the invention may be applied inthe case of repairs of endoscope optical systems comprising a singlethin broken gradient rod lens, because it is then possible to shortenthe dimensions of the two broken pieces in such manner that a singlegradient rod lens may be inserted between the two broken pieces whilstre-establishing the original length. To this end, the ends of the brokenpieces which are ground plane, may be bonded to the intermediate rod ora small gap may be provided.

The invention is described in particular in the following with referenceto the accompanying drawings, in which preferred embodiments of theinvention are diagramatically illustrated.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the diagrammatically illustrated structure of an endoscopeoptical system according to the invention;

FIG. 2 is an enlarged view of the distal section of the endoscopeoptical system of FIG. 1;

FIG. 3 shows a part length of the optical system of FIG. 1 with twogradient rod lenses which are to be strung together, and

FIGS. 4 and 5 respectively show the ocular section of the gradient rodlens optical system with two different constructions of the proximalgradient rod lens.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The endoscope optical system according to the invention comprises anobjective lens 1 which is bonded to a first gradient rod lens 2, and anumber of single subsequent gradient rod lenses 3, with a terminalocular lens 4. The rods lenses are strung together in loose form, with asmall spacing. The lengths of the individual gradient rod lenses 3 maybe selected freely as a function of the individual intermediate imagespacings. It is advantageous however to adapt the lengths of thegradient rod lenses to the intermediate image spacing, so that theseparation between every two adjacent rod lenses is centrally situatedbetween two intermediate images with optimum precision, since the beamsarriving from an image dot then have the greatest amplitude of thesinusoidal beam course, or rather the greatest divergence. The image asa whole thereby incurs minimum percentage interference from possibledust particles or the like. Apart from the identical lengths of thegradient rod lenses 3, the length of the gradient rod lens 2 at thedistal and proximal extremities should be selected as being no more thanhalf the spacing of two intermediate images.

If there are points along the length of the endoscope optical systemwhich are particularly vulnerable to breakage, the points of separationbetween the individual gradient rod lenses may be situated at thesepoints, that is to say thanks to the fact that the rod lengths areselected under consideration of the laws of optics.

It is appropriate furthermore to upgrade the end faces 5 of the gradientrod lenses by application of thin coatings, to reduce reflection.Furthermore, the marginal edges 6 of the end faces 5 are produced infacet-like form, to prevent breaking off of the gradient rods, and it isadvantageous to finally close off the spacing between two rod lenses byan annular joint in each case, to prevent precipitations of dustparticles on the end faces 5.

If the length of the gradient rod lengths is matched to the spacingbetween two intermediate images and the points of separation liecentrally within an intermediate image spacing and if the overall lengthof the rod length 2 and 3 is equal to the overall length of theintermediate image spacings, the final intermediate image 7 is generatedat the extremity of the last proximal rod lens, according to FIG. 4. Ifthe overall length of the rod lenses is smaller than an integralmultiple of the intermediate image spacing, the last proximalintermediate image is generated in enlarged form behind the lastproximal rod lens 3. If this embodiment according to FIG. 5 is selected,the ocular lens 4 may be constructed in simplified and thus less costlyform, corresponding to the image magnification by means of the rod lensoptical system.

If the diameter of the gradient rod lenses 3 is chosen comparativelysmall, the image angle of conventional objective lenses is commonly toosmall. According to FIG. 1, the objective 1 may be constructed as anegative lens, a meniscus lens or a planoconcave lens, so that theangular field may thereby be enlarged to 70° to 80°, for example.

I claim:
 1. An endoscope optical system comprising an objective lens, anocular lens and an image transmitter, comprising interposed rod lensestherebetween forming a plurality of intermediate images, wherein saidimage transmitter comprises a series of aligned individual gradient rodlenses which are positioned with minimal spacing between them and whoselengths each terminate between two said intermediate images.
 2. Anendoscope optical system as claimed in claim 1, wherein the lengths ofintermediate gradient rod lenses in said series is equal to that of thespacing between said intermediate images, wherein said intermediategradient rod lenses terminate centrally between two said intermediateimages, and wherein the gradient rod lenses at the proximal and distalends of said series have no more than half the length of saidintermediate image spacing.
 3. An endoscope optical system as claimed inclaim 1, wherein said gradient rod lenses have end faces with marginaledges which are provided with a facet and wherein the space between eachtwo adjacent gradient rod lenses is closed off by a ring mounting.
 4. Anendoscope optical system as claimed in claim 1, wherein an enlargedfinal intermediate image is formed outside the last proximal gradientrod lens nearest said ocular lens:
 5. An endoscope optical systemcomprising an objective lens, an ocular lens and an image transmitter,said image transmitter forming a plurality of intermediate images andbeing interposed between the objective lens and ocular lens, said imagetransmitter comprising a series of aligned individual gradient rodlenses being positioned with minimal spacing therebetween, said seriesincluding a proximal rod lens, a distal rod lens and a plurality ofintermediate rod lenses, each of the rod lenses having a length lessthan the distance between two intermediate images.
 6. An endoscopeoptical system according to claim 5, wherein the proximal gradient rodlens of the series has a length less than half of the intermediate imagespacing so that an enlarged, final intermediate image is formed thereby,said ocular lens being constructed to receive this enlarged finalintermediate image.
 7. An endoscope optical system as claimed in claim5, wherein the length of the intermediate gradient rod lens in saidseries is equal to that of the spacing between said intermediate images,said intermediate gradient rod lenses terminating centrally between twointermediate images, and the proximal and distal gradient rod lenseshaving a length of no more than half the length of said intermediateimage spacing.
 8. An endoscope optical system comprising an objectivelens, an ocular lens and an image transmitter, which form a plurality ofintermediate images, being interposed between said objective lens andocular lens, said image transmitter being a series of aligned individualgradient rod lenses which have end faces with marginal edges which areprovided with facets, each of said rod lenses having a length toterminate between two intermediate images and each space between twoadjacent gradient rod lenses being closed off by a ring mounting.